Janus particles for oil–water separation have attracted widespread attention in recent years. Herein, we prepared a bowl-shaped Janus particle that could rapidly separate oil and water through a thiol–ene click reaction and selective etching. Firstly, snowman-like composite microspheres based on silica and mercaptopropyl polysilsesquioxane (SiO2@MPSQ) were prepared by a hydrolytic condensation reaction and phase separation, and the effects of the rotational speed and molar ratios on their microscopic morphologies were investigated. Subsequently, bowl-shaped Janus particles with convex hydrophilic and concave oleophilic surfaces were prepared via a thiol–ene click reaction followed by HF etching. Our amphiphilic bowl-shaped Janus particles could remarkably separate micro-sized oil droplets from an n-heptane–water emulsion with a separation efficiency of >98% within 300 s. Based on the experimental and theoretical results, we proposed the underlying mechanism for the coalescence of oil droplets upon the addition of the amphiphilic bowl-shaped Janus particles.